The invention relates to a process and to devices for chemically hardening glassware, preferably hollow glassware, by the exchange of alkali ions between the surface of the glass and molten alkali salts.
Productivity arrangements according to the immersion process require large expenditures for the device. One is forced to work with relatively large amounts of molten salts, thereby requiring extensive safety precautions. This results in limitations to the economy of the process together with the resulting unsatisfactory degree of utilization. Certain solutions of the immersion process have the disadvantage that a reduction of compressive stress, developed in the surface layer which is caused by relaxation processes, occurs when the glassware remains within the furnace after removal from the salt bath or when moving from one bath to another. Processes where the glass products are sprinkled with molten salts show advantages because they lower expenditures for the device and are coupled with considerable improvement in degree of utilization.
No solutions have yet been proposed for the process of hardening hollow glassware products by rinsing with molten salt. Known proposed processes and devices concern only the treatment of plate glass or similar products. None of the proposed processes contain entire solutions for the processes and and devices, (such as by circulation of the molten salt), for the regulation of the salt stream, for insuring uniform wetting of the glassware and for the conveying devices. No economic solution for small glassware has been presented.
The object of the invention is to find possibilities for widening the use of ion exchange treatment of glassware and to improve the economy of such processes. The invention is based upon the task to chemically harden hollow glassware by rinsing with a molten salt and to propose complete solutions for devices used in the process.